fix(MusicSheetCalculator.ts): shorten lyrics y offset
fix(MusicSheetCalculator.ts): shorten lyrics y offset

shortened lyrics y offset below the staff.
now lyrics much better belong to the corresponding staff visually,
as with physical sheet music editions.

opensheetmusicdisplay/opensheetmusicdisplay,opensheetmusicdisplay/opensheetmusicdisplay,opensheetmusicdisplay/opensheetmusicdisplay